1. Field of the Invention
The present invention relates to a method for manufacturing titanium or titanium alloy clad steel plate.
2. Description of the Prior Art
A clad metal plate is manufactured by laminating two metal plates or more and joining the laminated metal plates to each other. This clad metal plate is excellent in corrosion resistance, wear resistance and heat resistance, and has a high strength. Therefore, the clad metal plate is widely used as an inexpensive material.
As the methods for manufacturing clad metal plate, an explosion bonding process, a surfacing process and a rolling process are pointed out. The rolling process, which can manufacture the clad metal plate of large area with high efficiency and at low cost, is most generally used.
In the rolling process, surfaces of cladding metals and a base metal, at which the cladding metals are bonded to the base metal, are cleaned, and the cladding metals and the base metal are laminated and hot-rolled or warm-rolled, by which the cladding metals are metallurgically bonded to the base metal. In this method, stainless steel as the cladding metal and carbon steel, low alloy steel and high alloy steel as the base metals are used.
However, when the rolling process is applied to the manufacture of a titanium clad steel plate, wherein titanium or titanium alloy is used as the cladding metal, it is extremely difficult to obtain a good joining property because there are problems as shown below.
When titanium or titanium alloy and alloy steel are laminated, uniformly heated at a predetermined temperature, and hot-rolled or warm-rolled, a brittle Ti-Fe intermetallic compound is generated on cladding surfaces by interdiffusion of titanium and iron. This brittle Ti-Fe intermetallic compound greatly decreases the shearing strength of the cladding surfaces.
As a method for preventing the intermetallic compound from being generated, a method, wherein a thin film or a foil of Mo, Nb or V which does not generate the intermetallic compound with titanium is employed as an insert material, has been proposed. The insert material is inserted between the base material and the cladding metal.
There are, however, two problems in the method for using the film or the foil of Mo, Nb or V. The first problem is that the manufacturing cost increases greatly because Mo, Nb and V are very expensive. The second problem is that since the insert material lacks ductility, the insert material breaks during rolling. Due to those problems, this method is not put to practical use.
Two sorts of insert materials which are manufactured on an experimental basis are pointed out. Plating and foil of Cu, Ni or Cr are disclosed in a journal "Metal" vol. 32, No. 20. A Japanese Patent Publication Laid Open No. 124483/85 discloses foil of stainless steel of ferrite and martensite. However, sufficient cladding strength cannot be obtained by those insert materials.
When the explosion bonding process is used instead of the rolling process, the Ti-Fe intermetallic compound is not generated since the cladding metal is bonded to the base material not metallurgically, but mechanically. In this method, a comparatively good cladding property can be obtained. However, since the explosion bonding process is limited to cladding of the cladding metals to the base metal of large area, it is difficult to use this process widely.